1. Field of the Invention
The present invention relates to a compact and fine thin-film heater with low power consumption, a method of manufacturing this thin-film heater, a tungsten film, and a method of manufacturing this tungsten film. Particularly, the invention relates to a thin-film heater using a tungsten film that is composed of tungsten in which both xcex1-phase tungsten and xcex2-phase tungsten exist, and a method of manufacturing this thin-film heater.
2. Description of Related Art
In recent years, micromachines have been extensively developed, and, along with this development, many devices have been designed with compact and fine structures. Many of these devices have heaters inside them. Recently, the heaters accommodated in these devices have been replaced by thin-film heaters that are advantageous in making these devices compact. Under these circumstances, thin-film heaters have also been required to be more compact and finer. As a device that uses a thin-film heater, a thermal printer is generally been widely known. In the field of thermal printers, research and development have also rapidly progressed to provide thin-film heaters in more compact and finer structures in order to achieve high definition printing.
When a thin-film heater is manufactured by forming a film of the heater using a material of a high heat-resisting property and a high resistivity, the thin-film film heater can be provided in a more compact and finer structure taking advantage of the characteristics of the high heat-resisting property. Further, based on the characteristic of high resistivity, the thin-film heater can secure a sufficient heating value despite having a compact and fine structure. Furthermore, the compact and fine structure makes it possible to minimize power consumption.
A Nichrome (Nixe2x80x94Cr) film has been known as a thin-film heater. The Nichrome film, however, does not have a sufficiently high heat-resisting property although it has a high resistivity. Therefore, this Nichrome film has had a drawback in that it becomes disconnected when it is provided in a compact and fine structure.
In order to eliminate the above drawbacks of the conventional example, it is an object of the present invention to provide a tungsten film that has a high heat-resisting property and a high resistivity, a method of manufacturing this tungsten film, a thin-film heater, and a method of manufacturing this thin-film heater.
It is another object of the invention to provide a tungsten film that can be formed in a compact and fine structure and that has a characteristic low power consumption, a method of manufacturing this tungsten film, a thin-film heater, and a method of manufacturing this thin-film heater.
It is still another object of the invention to provide a tungsten film that has high reliability and stable characteristics, a method of manufacturing this tungsten film, a thin-film heater, and a method of manufacturing this thin-film heater.
In order to achieve the above objects, according to a first aspect of the present invention, there is provided a tungsten film which is formed by an RF sputtering method, and is composed of tungsten having peaks at approximately 36 degrees, 40 degrees and 44 degrees in Bragg angle 2xcex8 of X-ray diffraction. Particularly, it is preferable that the tungsten film is composed of tungsten having coexisting xcex1-phase tungsten and xcex2-phase tungsten, and that the resistivity immediately after film-forming is within a range from 60 to 70 xcexcxcexa9cm, and the resistivity after a heat treatment is within a range from 55 to 65 xcexcxcexa9cm.
Further, according to a second aspect of the invention, there is provided a method of manufacturing a tungsten film that comprises a step of maintaining a density of residual oxygen molecules, in the atmosphere within a device, within a range from 3.54xc3x97109 to 1.77xc3x9711 (molecule/cm3), and a step of forming the tungsten film by an RF sputtering method within the device.
Further, according to a third aspect of the invention, there is provided a thin-film heater having a tungsten film formed on a substrate, wherein the tungsten film generates heat when a current is supplied to the tungsten film. It is preferable that the tungsten film is formed by an RF sputtering method, and that the tungsten film is constructed of tungsten having peaks at approximately 36 degrees, 40 degrees and 44 degrees in Bragg angle 2xcex8 of X-ray diffraction.
Further, according to a fourth aspect of the invention, there is provided a method of manufacturing a thin-film heater that comprises a step of setting a density of residual oxygen, within a device that carries out sputtering, to within a range from 3.54xc3x97109 to 1.77xc3x971011 (molecule/cm3), and a step of forming a tungsten film by an RF sputtering method within the range of the density of residual oxygen. Particularly, it is preferable that the method of manufacturing a thin-film heater further comprises a step of photolithography processing for patterning a photosensitive material on the tungsten film by using a photolithography method, a step of etching processing for etching the tungsten film to the shape of the photosensitive material, and a step of detaching the photosensitive material from the tungsten film.